A cartilage tissue of a vertebrate has certain physical properties such as slight elasticity and toughness, and is able to produce lubrication and cushioning effects when the vertebrate's joint is in active condition. Hence, movement of the vertebrate's joint can occur smoothly, and the cartilage tissue also provides support and protection to a bone tissue at the vertebrate's joint. The cartilage tissue is mainly composed of chondrocytes, a large amount of extracellular matrix including collagen and proteoglycan, and fibers.
As shown in FIG. 1, when the cartilage tissue gets damaged due to long-term wear, a conventional therapeutic method to repair the damaged cartilage tissue is to fill a damaged portion of the cartilage tissue with a collagen membrane 11 having a shape complementary to the damaged portion. However, since the collagen membrane 11 filled in the damaged portion is not in connection with the bone tissue, the collagen membrane 11 cannot be securely fixed to the damaged portion of the cartilage tissue and may even be detached therefrom. That is, integration of the collagen membrane 11 into the damaged portion of the cartilage tissue of the injured part of a living body is relatively poor.
FIG. 2 illustrates a conventional bone implant 12 adapted for filling a damaged portion 200 of a bone 2. The bone 2 includes a bone tissue 21 and a cartilage tissue 22 wrapping the bone tissue 21. The conventional cartilage implant 12 not only fills the damaged portion 200 to repair the cartilage tissue 22, but also fixedly extends into the bone tissue 21 to enhance the fixing of the conventional bone implant 12 to the bone 2. However, the conventional bone implant 12 has only the cartilage repair function and still wears out after a long-term use. Besides, the conventional bone implant 12 is not sufficiently compatible with the cells of the bone 2, and thus is unable to provide regeneration function for the cartilage tissue. Furthermore, friction may be generated between the bone implant 12 and the portion of the cartilage tissue 22 around the bone implant 12, which may result in fibrosis and poor lubricity of the cartilage tissue 22.
FIG. 3 shows another conventional bone implant 13 that includes at least one scaffold 131 disposed on a surface of the bone tissue 21 and connected to the cartilage tissue 22, and a chondrocyte layer 132 supported on the scaffold 131. By way of the chondrocyte layer 132, efficiency and success rate of repairing the cartilage tissue 22 can be improved. Although the conventional bone implant 13 has cartilage repair function, the scaffold 131 does not extend into the bone tissue 21 and is only connected to a portion of the cartilage tissue 22 adjacent thereto. Hence, bonding strength of the conventional bone implant 13 to the bone is being doubted. Besides, the cartilage tissue 22 is limited to a two-dimensional growth by extending along a surface of the cartilage tissue 22. Consequently, the cartilage tissue 22 may develop into a fibrous cartilage with poor lubricity instead of the expected hyaline cartilage with good lubricity.